MCTominay played the lone holding role against Liverpool, Crystal palace, Southampton and did quite well. He was terrific against Liverpool and Crystal palace most especially. So yes, he can play the holding midfield role quite well. One thing I would give him is his intelligence and positioning discipline. And I disagreed with the opinion that Declan Rice is a better passer than MCTominay. Both don't seem to have the range of passing nor offers creativity in the middle. They're no different from each other in this department eventhough I saw MCTominay making some vertical passes in between the lines, albeit short passes against Crystal palace. I would prefer we stick with MCTominay and continue to groom him. I bet if MCTominay was a regular for a small EPL club like Declan, we would all be swarming around him like bees as well.
Declan isn't better than Matic. He doesn't even have Matic's range of passing and spatial awareness to begin with. Matic at his best is no different from a withdrawn playmaking no 6 such as De Rossi. But unfortunately, his legs are not what it used to be. As for MCTominay, we don't know his ceiling yet. From what he's shown, Declan isn't better than him. MCTominay has gone up against world-class Verratti and has done well compared to Declan who's still a local champion. I learnt he even had a poor performance in his last match.